The present invention relates to a liquid crystal display device, in particular, to a packaging structure in which a liquid crystal display panel and a circuit substrate which supplies a drive voltage and a drive signal as liquid-crystal-drive signals are mounted to a liquid crystal display device.
Conventionally, a TCP (tape carrier package) or COG (chip on glass) packaging technique is used to mount, to a liquid crystal display device, a liquid crystal panel and a circuit substrate, drive IC, etc. which supply a drive signal and a drive voltage as liquid-crystal-drive signals to the liquid crystal panel.
According to TCP packaging, as shown in FIG. 11, a liquid crystal panel 101 is connected to flexible substrates (hereinafter, will be referred to TCPs) 102 carrying a liquid crystal drive IC thereon, and receives a drive voltage and a drive signal from the liquid crystal drive IC mounted to the TCPs 102.
Each TCP 102 receives an external drive voltage and drive signal via the circuit substrate 103 connected to the TCP 102 opposite to the panel.
The circuit substrate 103 for use with a TCP technique requires numerous input signal lines to transmit the drive voltage and the drive signal to the TCPs 102. Therefore, the circuit substrate 103 is normally fabricated from a multilayer plate including four to eight conductor layers and measures 5 mm to 10 mm in width and 0.6 mm to 1 mm in thickness.
As described above, according to a TCP technique, numerous lines are needed to transmit the drive voltage and the drive signal to the TCPs 102 via the circuit substrate 103 for use with the liquid crystal display device; therefore, the circuit substrate 103 is either bulky, or compact but costly due to multilayer wiring or other special techniques involved.
Japanese Laid-Open Patent Application No. 8-146449/1996 (Tokukaihei 8-146449; published on Jun. 7, 1996) discloses another packaging structure, which is an application of a TCP technique. This packaging structure is similar to conventional TCP techniques in that there are provided TCPs in the peripheral part of a liquid crystal panel and also that flexible wiring substrates are lined along the outer edge of a row of TCPs. The distinction lies where the wires on the flexible wiring substrates and the wires on the TCPs are connected to each other in the gaps between the TCPs in this structure, while they are connected in the gaps between the flexible wiring substrates and the TCPs according to conventional techniques. This structure thus enables reduction in dimensions of the peripheral part (frame) of the liquid crystal panel.
The arrangement is equivalent to a packaging structure used in a conventional TCP technique, with an only change in the location of the area where the wires on the flexible wiring substrates and the wires on the TCPs are connected to each other. The disclosed structure therefore cannot reduce the number of wires formed on the flexible wiring substrates. Besides, the wires on the flexible wiring substrates need additional length, in comparison to conventional wires, so as to reach the gaps between the TCPs. If the flexible wiring substrates need to be further elongated to suit increased dimensions of the panel, the drive signal and the drive voltage are likely to deteriorate during transmission. The issue will be elaborated again later.
Meanwhile, according to a COG technique, as shown in FIG. 12, liquid crystal drive ICs 112 and circuit substrates 113 for supplying a drive voltage and a drive signal to the liquid crystal drive ICs 112 are disposed in the peripheral part of a glass substrate 111a constituting a liquid crystal panel 111.
As described above, according to a COG technique, the circuit substrate 113 supplies a drive voltage and a drive signal to the liquid crystal drive ICs 112; therefore, the circuit substrate 113 can be readily connected to the liquid crystal panel 111.
As mentioned earlier, packaging of panels, which are becoming increasingly larger, using a TCP technique cause the drive signal and the drive voltage to decay during transmission. The decay occurs because the drive signal and the drive voltage are provided externally and must be passed through an area (supply point) which is located, for example, near a corner of the liquid crystal panel on the flexible wiring substrate, before being applied to the TCPs via the wires on the wiring substrates. The longer distance the drive signal and the drive voltage need to propagate from the supply point to the TCPs, the further they decay. Such deterioration does not occur in a liquid crystal display device with an about 10-inch display under typical conditions. The drive signal, however, cannot be transmitted in a 15-inch or larger liquid crystal display device, because the distance grows between the TCPs located at both ends, and the resultant large resistance of the wires on the flexible wiring substrate causes a large voltage drop.
If the drive signal can be successfully transmitted to all the TCPs in a 15-inch or even larger liquid crystal display device, there is a further problem: the drive voltage is more likely to decay and more difficult to transmit properly than the drive signal. To address this problem, a separate circuit substrate becomes necessary to supply a drive voltage to TCPs. This inevitably requires more investment in manufacturing machines and results in higher manufacturing cost in the manufacture of liquid crystal display devices.
Meanwhile, according to the aforementioned COG technique, as shown in FIG. 12, the circuit substrate 113 supplies the drive voltage and the drive signal to the liquid crystal drive ICs 112. The circuit substrate 113 can be readily connected to the liquid crystal panel 111 in an about 10-inch liquid crystal display device. It can, however, be connected to them only with difficulties in a 15-inch or larger liquid crystal display device due to the increased dimensions of the circuit substrate 113.
Besides, in the COG technique, the liquid crystal drive IC 112 and the circuit substrates 113 are connected to the peripheral part of the liquid crystal panel 111. This structure increases the total dimensions of the liquid crystal display device only without ever contributing to an increase in the screen size.
To address these problems, the present invention has an object to offer a liquid crystal display device of such a packaging structure that a drive voltage can be supplied to TCPs without being affected adversely by a voltage drop caused by an increased resistance of wires despite a growth in size of a liquid crystal panel.
To achieve the object, a liquid crystal display device in accordance with the present invention includes a liquid crystal panel in which a liquid crystal is interposed between two substrates on which drive electrodes for driving the liquid crystal are provided,
the liquid crystal panel including:
electrode-connecting-terminal sections (TCPs) each connected to a predetermined number of the drive electrodes and provided with drive means which is capable of driving the predetermined number of the drive electrodes; and
a circuit substrate for supplying a liquid-crystal-drive signal to the electrode-connecting-terminal sections,
wherein:
connecting wires are provided between a pair of adjacent electrode-connecting-terminal sections so as to transmit the signal supplied by the circuit substrate sequentially from one electrode-connecting-terminal section to a next; and
stabilizer means is provided between at least a pair of adjacent electrode-connecting-terminal sections so as to stabilize the signal transmitted via the connecting wires.
According to the arrangement, stabilizer means is provided to stabilize the signal transmitted via the connecting wires connecting adjacent electrode-connecting-terminal sections. Therefore, the liquid crystal display device is not affected adversely by a voltage drop caused by an increased resistance of wires despite the increased dimensions of the liquid crystal panel and the resultant increased distance between electrode-connecting-terminal sections. In other words, a signal can be now supplied to the electrode-connecting-terminal sections without being seriously affected by a voltage drop caused by an increased resistance of wires despite the increased dimensions of the liquid crystal panel.
To achieve the object, another liquid crystal display device in accordance with the present invention includes a liquid crystal panel in which a liquid crystal is interposed between two substrates on which drive electrodes for driving the liquid crystal are provided,
the liquid crystal panel comprising:
electrode-connecting-terminal sections each connected to a predetermined number of the drive electrodes and provided with drive means which is capable of driving the predetermined number of the drive electrodes; and
a circuit substrate for supplying a drive signal and a drive voltage as liquid-crystal-drive signals to the electrode-connecting-terminal sections,
wherein:
connecting wires are provided between a specific pair of adjacent electrode-connecting-terminal sections so as to transmit the drive signal and the drive voltage sequentially from one electrode-connecting-terminal section to a next; and
stabilizer means is provided between at least a pair of adjacent electrode-connecting-terminal sections so as to stabilize the drive voltage transmitted via the connecting wires, and provides the drive voltage as the liquid-crystal-drive signal to two electrode-connecting-terminal sections which are immediately adjacent to the stabilizer means, and also, through transmission via the connecting wires, to the other electrode-connecting-terminal sections which are electrically connected to the stabilizer means.
According to the arrangement, the drive voltage as a liquid-crystal-drive signal is prevented from decaying, as it is supplied collectively. Under these circumstances, the stabilizer means may be disposed as far down as immediately before the drive voltage and the drive signal transmitted to the TCPs falls below a tolerable decay value. The stabilizer means may be provided in various numbers and positions depending on the dimensions of the liquid crystal display device and other factors; a larger panel increasingly requires the drive voltage to be supplied collectively by the use of the stabilizer means.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, are not in any way intended to limit the scope of the claims of the present invention.